Efficient visible light photo-Fenton-like degradation of organic pollutants using in situ surface-modified BiFeO_3 as a catalyst

The visible light photo-Fenton-like catalytic performance of BiFeO3 nanoparticles was investigated using Methyl Violet （MV）, Rhodamine B （RhB） and phenol as probes. Under optimum conditions, the pseudo first-order rate constant （k） was determined to be 2.21 × 10^-2, 5.56 × 10^-2 and 2.01 × 10^-2 min〈 for the degradation of MV （30 μmol/L）, RhB （10 μmol/L） and phenol （3 mmol/L）, respectively, in the BiFeO3-H202-visible light （Vis） system. The introduction of visible light irradiation increased the k values of MV, RhB and phenol degradation 3.47, 1.95 and 2.07 times in comparison with those in dark. Generally, the k values in the BiFeO3- H202-Vis system were accelerated by increasing BiFeO3 load and H202 concentration, but decreased with increasing initial pollutant concentration. To further enhance the degradation of pollutants at high concentrations, BiFeO3 was modified with the addition of surface modifiers. The addition of ethylenediamineteraacetic acid （EDTA, 0.4 mmol/L） increased the k value of MV degradation （60 μmol/L） from 1.01 × 10.2 min^-1 in the BiFeO3-H202-Vis system to 1.30 min^-1 in the EDTA-BiFeO3-H2O2-Vis system by a factor of 128. This suggests that in situ surface modification can enable BiFeO3 nano-particles to be a promising visible light photo-Fenton-like catalyst for the degradation of organic pollutants.

Removing lignin model pollutants with BiFeO_3–g-C_3N_4 compound as an efficient visible-light-heterogeneous Fenton-like catalyst

BiFeO3-g-C3N4 nanoscaled composite was prepared with a hydrothermal method and evaluated as a highly efficient photo-Fenton like catalyst under visible light irradiation. The BiFeO3-g-CHN4 composite exhibited much stronger adsorption ability to lignin model pollutant （guaiacol） than that of BiFeO3, which may be due to the higher specific surface area （BiFeO3-g-C3N4：35.59 m2/g 〉 BiFeO3：7.42 m2/g） and the adsorption form of π-π stack between g-C3N4 and guaiacol. The composite exhibited excellent visible light-Fenton like catalysis activity, being influenced by the solution pH value and the proportions of BiFe03 and g-C3N4 nanosheets. Under optimal conditions with visible light irradiation, the BiFeO3- g-C3N4 composite yielded fast degradation of guaiacol with an apparent rate constant of 0.0452 rain-I, which were 5.21 and 6.80 folds of that achieved by using BiFeO3 and the mixture of BiFeO3 and g-C3N4 nanosheets, respectively. The significantly enhanced visible light-Fenton like catalytic properties of the BiFeO3-g-C3N4 composite in comparison with that of BiFeO3 was attributed to a large surface area, much increased adsorption capacity and the semiconductor coupling effect between BiFe03 and g-C3N4 in the composite.

纳米铁酸铋及其改性物的环境催化性能

铁酸铋(BiFeO_3)是一种典型的钙钛矿型氧化物,具有一定的可见光催化和多相类芬顿催化性能。在可见光照射且存在过氧化氢的情况下,BiFeO_3可活化过氧化氢并产生强氧化性物种,这些物种会攻击污染物分子从而使其降解。但BiFeO_3量子效率不高,光生电子和空穴容易复合;其活化过氧化氢的能力也有待提高。本文综述了近二十年来铁酸铋及其改性物作为可见光催化剂及多相类芬顿催化剂的研究进展,重点介绍了在制备过程中对其形貌的调控、贵金属沉积、离子掺杂、半导体复合、或负载于其他材料表面等改善其环境催化性能方法与效果,改性后发现BiFeO_3的可见光催化和多相类芬顿催化性能均得到提升。最后,对铁酸铋复合催化剂未来的发展方向进行了展望。